Defy gravity or cheat the wind? CW investigates to uncover the Holy Grail of two-wheeled speed
Writing bike reviews used to be very simple. For decades — probably most of 100 years — you could earnestly discuss stiffness, vibration damping or handling, and all the time know that the only thing anyone was going to look at was the weight of the bike.
Weight was the whole game because, well, clearly the lighter the bike, the faster it would go. It was a simple, one-stop number for cycling excellence.
The irony was that there wasn’t even much variation. In the 1900s a racing bike weighed 13kg, and by the 1950s this was down to around 10kg, where it stayed until the arrival of aluminium and carbon-fibre in the 1990s. Within each generation the weights from maker to maker were almost identical, because all bikes were built using essentially the same steel tubing and the same components.
That didn’t discourage anyone. You could drop a few grams by drilling holes in any areas where you thought the bike was excessively sturdy. You could mortgage your children and buy some lightweight bottle-cage bolts. When Eddy Merckx used a titanium stem for his Hour Record bike in 1972, riders all over the world went weak at the knees. Of course in terms of actual speed, on a flat track the few grams saved made a difference so small it was not measurable by any normal method.
Meanwhile it was perfectly obvious that unless you were climbing, the way to really go faster was a low, tucked riding position. Everyone knew this, but no one really tried to develop the idea.
The changes started in the 1980s. In 1984, the Italian Francesco Moser broke Merckx’s Hour record using disc wheels, a skinsuit and an aero helmet. All three quickly became time trial must-haves.
In 1989, Greg LeMond bolted a pair of the first Scott aero bars onto his time trial bike to win the Tour de France’s final time trial, and with it his second overall title. LeMond’s win prompted wholesale changes in riding position as aero bars made time triallists lower and narrower. The gains were massive — not seconds but minutes.
In 1992, Chris Boardman moved the goalposts into the next county when he went to a wind tunnel to develop the most refined riding position yet, then combined it with the extraordinary monocoque Lotus 108 ‘superbike’. He won the Olympic pursuit title at a canter.
The rest of the 1990s was a free-for-all. New materials in bike building — aluminium and carbon-fibre — meant that it was open season on both weight and frame shape, and most bike manufacturers didn’t know what to try next. There were superlight aluminium frames with a lifespan of a season, and a ride quality so bad you had to stand up the whole way. There were oversized and under-engineered carbon aero frames with the weight of a lorry and the structural integrity of a drinking straw.
The problem was that, unlike weight, aerodynamic drag is difficult to measure. It was almost impossible for a manufacturer, never mind a consumer, to make a realistic balance of the costs and benefits of the additional material needed to produce an aero profile. Wind tunnel testing was still rare, and even when it was used, it was as often as not done badly. There were some great bikes — notably from Lotus and the small, now-defunct British maker Hotta — but there were some terrible ones too.
In 2000, the UCI introduced a minimum weight for bikes: 6.8kg. It was a safety measure, intended to discourage extreme designs. But by drawing a line under weight as a battlefront, it focused interest on aerodynamics. Companies like Trek started committing time and money to wind tunnel development of properly aero TT bikes. Cervélo did the same, and scored a hit when Laurent Jalabert rode an early example of the then-radical P3 frame to a very unexpected second place (behind Lance Armstrong on his Trek) in the Tour de France prologue of 2002.
The decade and a bit since has been 90 per cent aero. First, it was the rest of the time trial set-up — better wheels, better aero helmets, and most recently better skinsuits. Then it was road kit — road bikes like Specialized’s Venge became aerodynamically more advanced than the TT bikes of only a few years earlier, while still being at minimum weight. Aero road helmets and jerseys have followed. The gains from this stuff are not trivial — at speeds over 30kph, an aero road helmet can be 1kph or more faster than a traditionally vented one, and at least the same again for a tight aero jersey.
There will only be more of it to come, especially since the UCI has signalled an intention to revise the equipment regulations next year, likely prompting widespread rethinking of bike design.
Of course, the UCI could also decide to reduce the required minimum weight. The most exciting days of bike development may yet be ahead of us.
Fine-tuning a road bike position
Time trial bikes and riders tend to hog the aero headlines, but even in the UK, with its huge time trial scene, most riders aren’t on a TT set-up. They’re on a road bike. So how does aerodynamics affect them?
Aerodynamic drag still matters more than you almost certainly think it does. If you ride a road bike on the flat at anything much over 10mph, aerodynamic drag is more than half of what slows you down. By 20mph, it’s almost all of what slows you down. Even a rider attacking on a 10 per cent hill could be expending a fifth of his energy overcoming wind resistance.
Happily, you can get most of the benefit by tweaking your position, because something like four-fifths of the drag is off the rider, not the bike.
For fast riding you can make big gains by dropping your head and shoulders lower over the bars, and getting your back as level as you can manage. The most efficient way to do this is by bending your elbows to around 90° and keeping your forearms parallel to the ground. Old-style TTers used the drops for this, but most current bikes are set up with lower bars, so it’s probably going to be about right if you keep your hands on the hoods.
The downside is that unless you do a lot of training in that position, your arms are going to hurt. The drops, while a little slower because the arms are straighter, might be more sustainable. Whichever you use, keep your elbows as far in as you can.
The next step is to shrug your shoulders in, if you can, and tuck your head down as far as you are able while still being able to see.
Freewheeling downhill, all of the same applies. But you might get a little more by moving your hands to the top of the bars, either side of the stem, and tucking down over them, elbows in. In general, for freewheeling, keep your thighs parallel — that is to say ‘a quarter-to-three’ with the pedals.
You could, of course, try descending on the top tube like Tony Martin, but it’s not a very stable position, and needs to be treated with a lot of caution.
How much might all this save? It does depend on the rider and the ride, but over a moderately hilly 100km ride, it could be five minutes or more over a normal position on the hoods.
You can gain a little more all round by avoiding loose, flapping clothing, not stuffing your pockets with capes and the like, and using an aero helmet.
Best for you
What works for you will be pretty personal; it’s down to your size and weight, and what sort of riding you’re doing.
Generally, lighter riders will probably want to pay a little more attention to bike weight, since it will be a bigger proportion of the total, and frame stiffness is less of a consideration, since it won’t have to cope with huge torque loads.
What kind of riding you do is, however, more important. If you’re mainly interested in sportive riding where your main objective is an overall time, always go for the aerodynamic option. However much time you might try to spend in a bunch, you’re essentially riding a time trial and, even on a very hilly course, aero will almost certainly win out. (Unless, of course, your main objective on the ride is just to stick it to your friends on the hills, in which case it’s weight all the way.)
If you’re a road racer, weight is more important, because the hills are usually where races are won and lost. There, you need to be able to climb competitively or you’re out of the game. But exactly how you balance weight and aero will still be dictated by your riding style. If you’re going to win anything other than a summit finish, you’ll still need the speed that only aero can give you to hold off the bunch, or to get the last half-inch in the sprint. You probably want a bike that complements your strengths, since that’s where the wins will come from.